The present invention pertains generally to thermoelectric devices and, more particularly, to a self-sufficient thermoelectric power supply that is specifically adapted to produce a relatively high-voltage power output such as for powering microelectronic devices.
The increasing trend toward miniaturization of microelectronic devices necessitates the development of miniaturized power supplies. Batteries and solar cells are traditional power sources for such microelectronic devices. However, the power that is supplied by batteries dissipates over time requiring that the batteries be periodically replaced. Solar cells, although having an effectively unlimited useful life, may only provide a transient source of power as the sun or other light sources may not always be available. Furthermore, solar cells require periodic cleaning of their surfaces in order to maintain efficiency of energy conversion.
Thermoelectric generators are self-sufficient energy sources that convert thermal energy into electrical energy according to the Seebeck effect—a phenomenon whereby heat differences may be converted into electricity due in large part to charge carrier diffusion in a conductor. Electrical power may be generated under the Seebeck effect by utilizing thermocouples which are each comprised of a pair of dissimilar metals (n-type and p-type) joined at one end. N-type and p-type refers to the respective negative and positive types of charge carriers within the material.
The temperature gradient that exists between the ends of the thermocouple may be artificially applied or it may be naturally-occurring as waste heat or as dissipated heat that is constantly rejected by the human body. In a wristwatch, one side is typically exposed to air at ambient temperature while the opposite side is exposed to the higher temperature of the wearer's skin. Thus, a small temperature gradient is present across the thickness of the wristwatch. A thermoelectric generator may be incorporated into the wristwatch to take advantage of the dissipated or waste heat and generate a supply of power sufficient to operate the wristwatch as a self-contained unit. Advantageously, many microelectronic devices that are similar in size to a typical wristwatch require only a small amount of power and therefore may also be compatible for powering by a thermoelectric generator.
The continuous development that is occurring in the microelectronics industry has led to the increasing miniaturization of certain electronic applications with a concomitant reduction in power consumption of many modern electronic devices. This reduction in power requirements for such electronic devices has enabled the employment of alternative energy sources such as thermoelectric generators.
When used as thermal energy harvesting devices for recovering thermal energy as dissipated heat which is typically lost to the environment, such thermoelectric generators may be utilized to power microelectronics or sensor systems. As the functional density of such modern electronic devices increases due in part to the integration of the many subcomponents that make up such electronic devices, power consumption of the devices has shrunk to the micro-watt and nano-watt level. Often however, a higher power is required for many microelectronic devices. This higher power requirement is often in the milli-watt range.
In view of the above-described developments in microelectronic miniaturization, there exists a need in the art for a power supply for such microelectronic devices that is capable of providing an essentially continuous supply of power thereto. Furthermore, there exists a need in the art for a power supply for microelectronic devices that does not require periodic replacement of the power source.
In addition, there exists a need in the art for a power supply for microelectronic devices that can provide a stable and efficient source of power thereto and which has an effectively unlimited useful life. Finally, there exists a need in the art for a power supply such as may be used for microelectronic devices that is capable of converting essentially constant energy sources into electrical energy using only small temperature gradients.